Don't think anyone sells slicks, you have to make your own. Grind all of the tread off with a dremel tool/sanding drum, till you have slicks. You'll have to experiment with different company's tires to see which rubber compound and carcass shape works best. Tires to start with would be: Proline Suburbs in MC or M4 compound( use the stock blue closed cell shaped inserts), Panter Switches in Clay compound (AKA inserts or Proline V3 1/8th closed cell iserts), AKA Wishbones or Subcultures in SuperSoft compound (stock inserts), or Hotbodies Beams (use proline V3 wide closed cell 1/8th inserts). You may not even want full slicks, if the track dries any or gets a little dust on the surface, you'll want shadow pin tires (leave a hint of tread when grinding them down)
IMO, hotbodies tires in their pink compound are the best tires for every class period. The Beams with V3 inserts are the most awesome tires for indoor SC.